Datasheet

AD9125
Rev. 0 | Page 46 of 56
300
250
200
150
100
50
0
0 12001000800600400200
f
DAC
(MHz)
POWER (mW)
09016-047
Figure 79. DVDD18 Power Dissipation vs. f
DAC
Due to Inverse Sinc Filter
300
250
200
150
100
50
0
50 300250200150100
f
DATA
(MHz)
POWER (mW)
1×
2×, 4×, 8×
09016-048
Figure 80. DVDD18 Power Dissipation vs. f
DATA
Due to Fine NCO
TEMPERATURE SENSOR
The AD9125 has a diode-based temperature sensor for measuring
the temperature of the die. The temperature reading is accessed
through Register 0x49 and Register 0x4A. The temperature of
the die can be calculated by
88
)925,47]015[( −
=
:TempDie
T
DIE
where T
DIE
is the die temperature in
o
C. The temperature
accuracy is ±5
o
C typical.
Estimates of the ambient temperature can be made if the power
dissipation of the device is known. For example, if the device power
dissipation is 800 mW and the measured die temperature is 50
o
C,
then the ambient temperature can be calculated as
T
A
= T
DIE
– P
D
× T
JA
= 50 – 0.8 × 20.7 = 33.4°C
where:
T
A
is the ambient temperature in
o
C.
T
DIE
is the die temperature in
o
C.
P
D
is the power dissipation.
T
JA
is the thermal resistance from junction to ambient of the
AD9125, as shown in Table 7.
To use the temperature sensor, it must be enabled by setting
Register 0x01, Bit 4, to 0. In addition, to obtain accurate readings,
the range control register (Register 0x48) should be set to 0x02.